1. Field of the Invention
The present invention relates to a safety switch for use in stopping machinery in any emergency so as to protect the operators against an accident which may result in injury or death.
2. Background Art
In factories or any sites where machinery is in operation, various types of safety switch are used so as to stop the machinery when any emergency occurs, or when a normally shut room door is carelessly left open or when a protective cover of the machinery is carelessly left open.
For example, PCT 90/08396 Publication (laid open on Jul. 26, 1990) discloses a safety switch using a pair of locking cams that are expanded sideways in response to the entry of an actuator. Japanese patent Publication (allowed) No. 1-24332 (published on May 11, 1989) discloses a safety switch also uses locking cams that are expanded in response to entry of an actuator. A disadvantage in common with these two prior art safety switches is that the body must be large enough to allow for the expansion of the arms.
The known switches are designed to shift a movable contact point from a fixed contact point to the other fixed contact point in accordance with the entry of an actuator but the problem is that deenergization is likely to occur before the door is completely locked.